1. Field of the Invention
The present invention relates to a planar light-emitting device, and more particularly, to a planar light-emitting device for gathering and mixing light to generate planar light.
2. Description of the Prior Art
A planar display such as a liquid crystal display (LCD) is a passive display, i.e., it requires a device functioned as a light source, to provide a planar or linear light, and this device is usually called a backlight module. There are usually two types of backlight modules, one is the direct type backlight, and the other is the edge light type backlight.
FIG. 1 illustrates a conventional direct type backlight module 101. The direct type backlight module 101 includes a set of light sources 11, a liquid crystal display panel (not shown), which being placed above the direct type backlight module 101, and an optical conditioning component 12, such as a diffuser and/or a prism sheet etc. The light sources 11, such as cold cathode fluorescent lamps (CCFLs), organic light emitting diode (OLED) or/and light emitting diodes (LEDs), are installed behind the liquid crystal display panel. The optical conditioning component 12 functions to direct and uniformly spread the light emitted by the light sources 11 into the liquid crystal display panel. The light sources 11 usually have to be spaced and arranged deliberately for uniformly distributing the light into the panel in order to avoid the occurrence of bright area 13 and dark area 14 as shown in FIG. 1.
FIG. 2 illustrates a conventional edge type backlight module 102. The edge type backlight module 102 includes at least a set of light sources 112, a liquid crystal display panel (not shown), an optical conditioning component 122, and a light guide plate (LGP) 152. In the edge type backlight module 102, the light sources 112 are installed on at least one edge of the light guide plate 152. The optical conditioning component 122 and the light guide plate 152 are for directing and uniformly spreading the light emitted from the light sources 112 into the liquid crystal display panel. Additionally, the light sources 112 may be CCFLs, OLED or/and LEDs, and the optical conditioning component 122 may be a diffuser and/or a prism sheet. The bigger the size of the liquid crystal display panel becomes, however, the more the numbers of light sources 112 are accordingly required, and the light sources 112 are necessarily installed on more edges of the light guide plate 152.
However, no matter which type of the backlight module is adopted, most of the light generated by the light sources 11/112 directly enters into the optical conditioning component 12/122 and/or the LCD panel. Whenever any variation of the light sources happens, such as blinking, failure, fading etc., the backlight module becomes unstable in brightness, and color shift phenomenon may occur.